The present invention relates to retry control (restart control) when an inverter trip of an inverter compressor occurs.
As an example of an inverter compressor, there is an inverter oil-cooled screw compressor. The oil-cooled screw compressor supplies a lubricant to a screw unit of the compressor. However, when the compressor stops, some of the lubricant remains inside a main body of the compressor. Therefore, when the compressor is started at a low temperature lower than, for example, the lower limit of a predetermined temperature, the viscosity of the lubricant which remains inside the main body of the compressor is increased so as to generate an excessive torque caused by compression of the lubricant immediately after the starting, thereby generating overcurrent to cause a trip in the inverter in some cases. Further, even in an oil-free compressor, the viscosity of a lubricant which remains in a bearing unit is increased when a main body of the compressor is started, which possibly causes generation of an excessive torque and an overcurrent trip of the inverter at the time of starting. Especially, a high-efficiency synchronous motor as a driving motor shows this tendency due to a small starting torque. As a related art of such retry control when the inverter trip occurs, is represented by Japanese Patent No. 3255213, titled “CONTROL METHOD FOR PACKAGE TYPE SCREW COMPRESSOR AND CONTROL DEVICE”.